1. Field of Invention
This invention relates to lubricating oil compositions comprising fuel oils, crude oils, mineral oils and synthetic oils having one or more improved characteristics, such as pour point, viscosity, viscosity index, metal-free and anti-wear properties.
Crude, refined and synthetic lubricating oils frequently require modification or the addition of additives to improve one or more of their physical characteristics such as pour point, viscosity, viscosity index, metal-free and anti-wear characteristics. In particular, one or more of the above-described properties is imparted to lubricating oil compositions by the addition of a dialkyl, diaryl, dialkaryl, diarylalkyl or diaryloxyalkyl dithiophosphorylated copolymer of (A) a monomeric aziridineethyl acrylate or methacrylate (B) a monomeric alkyl acrylate or alkyl methacrylate. The copending application of Pellegrini et al, entitled Dithiophosphorylated Copolymers of Aziridineethyl Acrylates or Methacrylates and Alkyl Acrylates or Methacrylates, Ser. No. 843,331, filed Oct. 18, 1977, describes in detail how to prepare these compounds.
2. Description of the Prior Art
The monomeric aziridineethyl acrylic and methacrylic esters and the monomeric alkyl esters of acrylic and methacrylic acid from which the copolymers are prepared are known. For example, the preparation of copolymers of aziridineethyl acrylates or methacrylates/alkyl acrylates or methacrylates and their use in crude oils, mineral oils and fuel oils are described in U.S. Pat. No. 3,864,099, issued to Ek, on Feb. 4, 1975. In particular, monomeric C.sub.8 -C.sub.18 alkyl esters of acrylic or methacrylic acid are described as particularly suitable for comprising of aziridineethyl acrylates or methacrylates using conventional techniques in the art. These compounds are described as enhancing one or more physical characteristics of the above oils when added thereto. U.S. Pat. No. 3,865,740, issued to Goldschmidt, on Feb. 11, l975, describes certain alkyl, aryl, alkaryl or arylalkyl O,O-diesters of dithiophosphoric acid which may serve as extreme pressure agents, antioxidants and ashless dispersants for lubrication oil compositions. Similarly dithiophosphoric acid esters and their derivatives are known and described for example, in U.S. Pat. No. 3,826,745, issued to Ryer et al, on July 30, 1974 which teaches dithiophosphoric acid ester derivatives in combination with amine salts of mixed acid phosphates as anti-wear, corrosion inhibitors and anti-oxidant additives for lubricating oils. These dithiophosphates are additionally described as suitable for use in various types of lubricating oil compositions, including animal and vegetable oil compositions as well as mineral and synthetic lubricating oils.